Unitary spinal disc implant

ABSTRACT

A unitary intervertebral device, having no moving components is provided for non-fusion articulation and fusion applications. The interbody articulating device allows for limited flexion and rotation between the implant and an adjacent vertebra, helping to preserve or restore near-normal motion between adjacent vertebrae. Rotational motion is achieved through one or more protrusions incorporated into the spinal interbody device. In one articulating form, a first protrusion extends perpendicularly from one bearing surface of the interbody device to form a rotational protrusion, while at least a second protrusion extends from the opposite bearing surface of the interbody device to form a non-rotational protrusion. In another form, a single protrusion extends axially from one bearing surface of the interbody device to form a spike or anchoring, rotating protrusion, while the opposite bearing surface may be slightly rounded and/or comprising a bone-ingrowth promoting surface. Similarly configured fusion salvage devices are also described.

CROSS-REFERENCE

This application is a continuation of U.S. application Ser. No.14/177,109, filed Feb. 10, 2014, which claims the benefit of priority toand incorporates by reference U.S. Provisional Application No.61/763,355, filed Feb. 11, 2013, entitled “Artificial Spinal DiscImplant” and U.S. Provisional Application No. 61/786,193, filed Mar. 14,2013, entitled “Artificial Disc Implant With Ligamentous Fixation SystemAnd Method Of Treating A Degenerated Spinal Segment”, all of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

Artificial disc technology has been employed as a surgical approach torepair or replace damaged spinal discs in an attempt to relievedebilitating neck and back pain, and to maintain or restoreintervertebral spacing while attempting to minimize their constrainingeffects on the normal biomechanical movement of the spine. The quest fora more physiologic device to accomplish these goals began in the 1950sand continues to this day.

Total disc replacement is still a relatively new, promising field ofspine implant technology that has the potential to revolutionize thetreatment of degenerative disc disease. It is clear from both short-termin-vitro and clinical data, that disc replacements can successfullypreserve the motion of a treated spine and significantly reduce thepotential incidence of adjacent level disc degeneration. Butunfortunately, not unlike as many as 40% of spinal fusions performedworldwide, disc replacements may also need to be revised due to poorimplantation technique, component wear, or failure of the device, toname but a few.

Clinical data has illustrated that many failures occur as a result ofover-aggressive bone bed preparation or excessive protuberances on theimplants both of which can result in compromise of the vertebralendplates. Other data suggests that many design failures resulted frompoint loading or inadequate load distribution across the endplate. Stillother designs suffer from poor choices of materials for articular wearbearings, oxidation, and/or inadequate long-term wear characteristicsbetween device sub-components. Each of the aforementioned deficienciesmay ultimately result in subsidence, loss of designed function, or evenspontaneous fusion.

It may be a generation before sufficient data emerges to clearlydelineate the long-term successful designs from the catastrophicfailures, but given that most of the currently pending or recentlyapproved artificial disc implants in the market are based on designfundamentals utilized in other orthopedic applications that have alreadybeen demonstrated to fail for predictable reasons, one might expect tosee many of these designs fail in similar fashion for the same reasons.Accordingly, there remains a need for better artificial disc technologythat addresses these shortcomings by providing an artificial disc thatdoes not significantly inhibit spinal movement, minimizes any potentialfor wear between disc components and or vertebral bodies, improves uponthe surgical technique utilized to implant them, reduces the potentialfor histocytic foreign body and/or inflammatory response, and providesphysiologic load bearing and joint spacing functions akin to the normal,healthy spinal disc. In addition, there also remains a need for bettersalvage and fusion devices to replace other failed artificial discs.

SUMMARY OF THE INVENTION

A unitary intervertebral device, having no independent moving componentsis provided for non-fusion articulation applications. The interbodyarticulating device allows for limited flexion and rotation betweenadjacent vertebrae, helping to preserve or restore near-normal motionbetween adjacent vertebrae. Rotational motion is achieved around one ormore protrusions incorporated into the spinal interbody device.

In one aspect the invention is an implant comprising a unitarystructure, having no independent articulating components, containingintegrated features to replace the articulating function of the naturalspinal disc, and allowing a spinal joint into which it has beenimplanted, to closely approximate the flexion biomechanics androtational motion of a reasonably healthy joint.

It is another object of this invention to provide a highly polished,high wettability surface finish to the arcuate surface(s) of adiscus-shaped implant which makes broad contact with the endplates ofthe vertebral bodies in order to improve rotational motion with reducedfriction and wear.

It is another object of this invention to significantly reduce oreliminate 3^(rd) body wear particles resulting from rolling or slidingfriction between the articulating surfaces of an artificial disc and thevertebral endplates and/or endplate cartilage of the spine.

It is another object of this invention to significantly reduce oreliminate any 3^(rd) body wear particles resulting from micro-motion orsliding friction between assembled sub-components of the artificial discsuch as between a poly bearing surface and an endplate to which it maybe captured, fixed or otherwise assembled.

It is another object of this invention to maximize the surface areacoverage of the vertebral endplate with the implant, to minimize thepotential for implant subsidence, spontaneous fusion, and localizedcompression stresses.

It is yet another object of at least one variation of this invention topreserve as much native endplate cartilage as possible to promote andimprove articulation between the vertebra and the implant, rather thanintentionally removing native cartilage and abrading endplate surfacesto induce bone ingrowth and fusion to the implant on one or bothadjacent endplate surfaces, as is done with other spinal discreplacements.

In one articulating form, a first protrusion extends perpendicularlyfrom the superior (first) aspect of a discus-shape of the interbodydevice to form a spike or rotational protrusion, while a secondprotrusion extends axially from the inferior (second) aspect of theinterbody device to form a second spike or rotational protrusion.Protrusions preferably extend perpendicularly from the apex of both thefirst and second arcuate articulating surfaces about the central axis.

In another form, a single protrusion extends axially from the superioraspect of the interbody device to form a spike, pivot point, oranchoring protrusion, while the inferior surface is a slightly roundedarticulating bearing surface. One or both of the first and/or secondarcuate surfaces may be highly polished.

In yet other variations, the implant is configured to provide a polishedarticulating surface on one bearing surface and a fusion surface on theopposite bearing surface.

In other articulating and non-articulating forms, tether features aredescribed for providing ingrowth through the endplate to an adjacentvertebral body.

In still other configurations, variations of a unitary device aredescribed comprising an intermediate core that is permanently affixedbetween the outer articulating bearing surfaces, to act as analternative cushioning apparatus, providing a dampening feature for thespine in place of the defective natural spinal disc. Both articulatingand fusion versions of the device are described.

Numerous geometries are described to define functional profiles of thedisc replacement implant which may be utilized, including regular andirregular Reuleaux polygons. Numerous variations of the disc replacementand methods of use are described.

Also described herein are similarly configured fusion salvage devicescomprising protrusions, tether features, ingrowth features and surfacegeometries.

Provided herein is a unitary implant adapted for placement betweenadjacent surfaces of a joint comprising: a first bearing surface and asecond bearing surface, wherein the first and second bearing surfacesare generally convex and configured to have generally spherical bearingsurface curvature that generally conforms to the concave geometry of theadjacent joint surfaces; an outer radial edge surface; a firstprotrusion on the first bearing surface, wherein the first protrusion isconfigured to contact a central portion of a first adjacent jointsurface, and wherein the first protrusion is adapted to allow rotationabout an axis.

In some embodiments, the unitary implant further comprises a secondprotrusion on the second bearing surface, wherein the second protrusionis configured to contact a central portion of a second adjacent surface,and wherein the second protrusion is adapted to allow rotation about thecommon axis of the first and second protrusion.

In some embodiments of the unitary implant, the first protrusion isconical. In some embodiments, the second protrusion is conical. In stillother embodiments the first protrusion or second protrusion may comprisea cone, a curved cone (sometimes referred to as parabolic or hyperboliccones), a truncated cone, or a cylinder. In some embodiments, theprotrusions are different. Still further, the first protrusion or secondprotrusion may comprise a truncated cone with a hole about the centralaxis, or a cylinder with a hole about the central axis. Still further,the hole in the protrusion may be a blind hole or a thru-hole thatpenetrates through the entire implant.

In some embodiments, the implant comprises a truncated cone with a holeabout the central axis, or a cylinder with a hole about the centralaxis, wherein the implant also comprises a tethering feature that isconfigured to promote ingrowth or attachment to the adjacent vertebra.In some embodiments, the attachment may be to just one adjacent endplateor vertebra: In other configurations, the attachment may be to both ofthe adjacent endplates or vertebrae.

In some embodiments, the first protrusion and/or the second protrusionis adapted to penetrate at least the cartilage of the first adjacentjoint surface and/or the second adjacent joint surface, providing anextremely conservative surgical procedure. In other embodiments, thefirst protrusion or the second protrusion is adapted to penetrate theendplate of the first adjacent joint surface or the second adjacentjoint surface.

In still other embodiments of the unitary implant comprising a firstprotrusion on the first bearing surface, the implant may furthercomprise at least a second and third protrusion on the second bearingsurface, wherein the at least second and third protrusion are configuredto contact a portion of a second adjacent surface, preferablypenetrating at least a portion of the adjacent endplate, and wherein theat least second and third protrusion are adapted to prevent movementbetween the second bearing surface and the second adjacent surface.

In some embodiments of the unitary implant, the implant is generallycircular in shape about a central axis. In other embodiments, theimplant is non-circular in shape about a central axis. In certainpreferred embodiments, the implant may comprises an elliptical planarshape or a common variant thereof.

Still further, in other preferred embodiments, the implant shape mayresemble a Reuleaux polygon planar shape comprising three or more sides.The Reuleaux polygon shape may be in the form of an irregular Reuleauxpolygon, wherein at least one side of the polygon is curved, or whereinat least one side has a different length than the remaining sides, orboth.

In some embodiments, the implant comprises an anatomic-like bearingsurface, wherein the curvature of the first bearing surface and thesecond bearing surface is generally spherical or near spherical. Inother embodiments, the curvature of the first bearing surface and thesecond bearing surface is generally multi-radial in order to moreclosely match the native, damaged or surgically prepared endplatesurface. In some embodiments, the first bearing surface and the secondbearing surface geometries are the same. Alternatively, in otherembodiments, the first bearing surface and the second bearing surfacecomprise different geometries.

Still further, in some embodiments the first bearing surface and thesecond bearing surface are mirrored, or symmetrical about a centraltransverse plane, whereas in other embodiments the first bearing surfaceand the second bearing surface are inclined to each other about acentral transverse plane to better match or reconstruct the naturallordosis (or kyphosis) of the spine.

In some embodiments of the implant, only the first bearing surface andthe first protrusion are polished articulating surfaces. In otherembodiments, only the second bearing surface and the second protrusionare polished articulating surfaces. In still others, all of the bearingsurfaces and protrusions are polished articulating surfaces.

In any one of the embodiments described herein, the first bearingsurface or second bearing surface may comprise or be manufactured fromat least one of the following materials: pyrolytic carbon, titanium,titanium nitride, tantalum, cobalt, chromium, polyethylene, PEEK®(Polyether ether ketone), Delrin®, alumina, zirconia, silicon carbide,silicon nitride, stainless steel, diamond, or a diamond like material.In some embodiments, the unitary implant may comprise a core fabricatedfrom one material having one set of properties, and an outer bearingsurface fabricated from another material having a different set ofproperties.

In some embodiments, the implant is an articulating implant, havingapplications in artificial limbs, robotics, or other joints andmechanisms. In some embodiments, the implant is a medical implant havingapplications for veterinary applications. In still other preferredembodiments, the implant is a human medical implant intended for thespine.

Provided herein is a unitary spinal disc implant adapted for placementbetween adjacent vertebral surfaces of a spinal joint comprising: afirst bearing surface and a second bearing surface, wherein the firstand second bearing surfaces are generally convex and configured to havea spherical curvature that generally conforms to the concave geometry ofthe adjacent spinal joint surfaces; an outer radial edge surface; afirst protrusion on the first bearing surface, wherein the firstprotrusion is configured to contact a central portion of a firstadjacent spinal joint surface, a second protrusion on the second bearingsurface, wherein the second protrusion is configured to contact acentral portion of a second adjacent spinal surface, wherein the firstprotrusion and second protrusion are adapted to allow rotation about acommon axis.

Provided herein is a method of using a spinal disc implant wherein themethod comprises providing a unitary disc implant adapted for placementbetween adjacent vertebral surfaces of a spinal joint, wherein theimplant comprises: a first bearing surface and a second bearing surface,wherein the first bearing surface and second bearing surface aregenerally spherical; a first protrusion on the first bearing surface,wherein the first protrusion is configured to contact a central portionof a first adjacent spinal joint surface; a second protrusion on thesecond bearing surface, wherein the second protrusion is configured tocontact a central portion of a second adjacent spinal surface; andwherein the first protrusion and second protrusion are adapted to allowrotation of the spinal disc implant about a common axis.

Provided herein is a unitary spinal disc implant adapted for placementbetween adjacent vertebral endplates comprising: a first bearing surfaceand an second bearing surface, wherein the first and second bearingsurfaces are configured to have a geometry that conforms to the concavegeometry of adjacent endplate surfaces; at least one conic protrusion onat least one bearing surface for penetrating at least one of theadjacent endplates, wherein the at least one protrusion is configured tocontact a central portion of at least one adjacent vertebral endplate.

In some embodiments, the first bearing surface is an articulatingsurface. In some embodiments, the second bearing surface is anarticulating surface. In some embodiments, the first bearing surface andsecond bearing surface geometries are the same. In some embodiments, thefirst bearing surface and second bearing surface comprise differentgeometries.

In some embodiments, the geometry of the first bearing surface and/orsecond bearing surface may be generally spherical. Alternately, thefirst bearing surface geometry may be generally flat to spherical.

In still other embodiments, the second bearing surface geometry isgenerally flat in the center, transitioning to spherical at the radialedges. Alternately the second bearing surface geometry may be generallyflat with radiused edges. Still further the second bearing surfacegeometry may be generally flat and transitioning to a proportionatelylarge spherical radius to replicate a worn or surgically preparedendplate surface. In even further embodiments, the first bearing surfaceand second bearing surface comprise slightly increasing arcuate radii ofcurvature from the outer [radial] edge surface to the central axis. Insome embodiments, the arcuate radii of curvature of the first and secondbearing surfaces are essentially mirror imaged about a centraltransverse plane.

In some embodiments, the first bearing surface and second bearingsurface are centered about a central axis. Further still, the at leastone conic protrusion is centered about the central axis. In otherembodiments, the at least one conic protrusion is located off-centerfrom the central axis.

In at least one embodiment, the first bearing surface and second bearingsurface are inclined to each other about a central transverse plane, inorder to provide the ability to restore the natural spinal lordotic orkyphotic curvature, wherein the anterior height of the implant may begreater than the posterior height (for restoring lordosis) or theposterior height of the implant may be greater than the anterior height(for restoring kyphosis).

In any one of the preceding embodiments, the implant is circular inshape about the central axis. Alternately, the implant is configured tobe elliptical in shape about the central axis, wherein the M/L dimensionis greater than the A/P dimension. Even further, the implant may bepolygon in shape about the central axis, wherein the polygon comprisesat least four side edges. Additionally, the polygon may have eitherstraight or curved sides, (alternately called a Reuleaux polygon), andmay also have sides with different lengths and smoothly blendedintersections.

Still further, in some embodiments, the implant comprises ananterior-posterior (front to back) dimension that is greater than theoverall arcuate height of the implant. This dimensional configurationcan be provided in a range and may be represented by a ratio wherein theanterior-posterior dimension to the overall arcuate height is at least1.01:1; is at least 1.1:1; is at least 1.2:1; is at least 1.5:1, or isat least 2.0:1; etc., for non-limiting example.

Further still, in some embodiments, the implant comprises amedial-lateral dimension that is greater than the overall arcuate heightof the implant. This dimensional configuration can also be provided in arange and may be represented by a ratio wherein the medial-lateraldimension to the overall arcuate height is at least 1.01:1; is at least1.1:1; is at least 1.2:1; is at least 1.5:1, or is at least 2.0:1; is atleast 3.0:1; is at least 4.0:1; etc., for non-limiting example.

In some embodiments, the implant comprises at least two protrusions. Inother embodiments, the implant comprises exactly two protrusions. Instill other embodiments, the implant comprises at least one protrusionon at least one bearing surface, wherein the at least one protrusion isconic. Still further, in some embodiments, the at least one conicprotrusion is a truncated cone comprising a base diameter with a widergirth and may further comprise an inner void. In those embodiments wherethe conic protrusion includes an inner void, the void may be a blindhole, or it may be a void that extends through the entire implant. Inpreferred embodiments the conic protrusions, and corresponding holes orvoids are concentric about a central axis.

In any one of the embodiments herein, the at least one protrusion isconfigured to puncture the adjacent endplate when the implant ispositioned between vertebrae.

In some embodiments, at least one of the first bearing surface and thesecond bearing surface comprises at least one fenestration. The at leastone fenestration may be circular or non-circular in profile, and/or ablind void or hole. The fenestration may comprise a ridge or a groove.Alternatively, more than one fenestration may be present, with eachhaving a different configuration.

In any one of the embodiments herein, at least one of the first bearingsurface and the second bearing surface is polished, wherein the at leastone polished bearing surface has a surface finish ≤4 RMS. In a preferredembodiment, the at least one of the first bearing surface and the secondbearing surface is an articulating surface.

In some embodiments, exactly one of the surfaces is an articulatingsurface and at least a portion of the other of the surfaces is atextured surface. In some embodiments, at least a portion of at leastone of the first surface and the second surface is textured.

Still further, in other embodiments, at least a portion of both thefirst surface and the second surface is textured. In one such preferredembodiment, both the first surface and the second surface is anon-articulating surface, wherein at least a portion of both of thefirst surface and the second surface is a fusion surface. In one suchpreferred embodiment, at least a portion of the first surface or thesecond surface comprises a surface finish ≥125 RMS.

In some embodiments, the implants are non-articulating salvage or fusionimplants, wherein both surfaces comprise a non-articulating texturedsurface, and wherein the textured surface is a surface configured toreceive a fixation compound. Alternatively, the textured surface is aporous surface intended to mimic cancellous bone and promote ingrowth.

Alternatively, a non-articulating surface may comprise one or morefenestrations, wherein a fenestrated surface is a surface configured toreceive a fixation compound.

In some embodiments, the implant is configured for use in anarticulating joint. In other embodiments the implant is configured foruse in the spine of an animal. In a preferred embodiment, the implant isconfigured for use in the spine of a human as a spinal disc implant. Ina most preferred embodiment, the implant is a unitary disc implant,having no moving components within the device.

Provided herein is an assembled disk-like implant adapted for placementbetween adjacent vertebral endplates comprising: a first endcap having afirst outer surface and first inner surface and a first outer radialedge; an second endcap having second outer surface and second innersurface and a second outer radial edge, an intermediate core comprisingan upper surface and lower surface configured to be permanently bondedbetween the first inner surface and the second inner surface; at leastone protrusion on at least one endcap surface, wherein the at least oneprotrusion is configured to contact a portion of at least one adjacentvertebral endplate.

In some embodiments, the first endcap surface and second endcap surfaceare each configured to have an external bearing geometry that conformsto the geometry of adjacent endplate surfaces.

In any one of the embodiments, the first inner surface and second innersurface is configured to mate with the intermediate core,

In some embodiments, the first outer surface is an articulating surface.In some embodiments, the second outer surface is an articulatingsurface. In some embodiments, both the first outer surface and thesecond outer surface are articulating surfaces.

In some embodiments, the first outer surface is a textured surface. Insome embodiments, the second outer surface is a textured surface. Insome embodiments, both the first outer surface and the second outersurface are textured surfaces.

In some embodiments, the first outer surface and second outer surfacegeometries are the same and comprise constant arcuate radii ofcurvature. In other embodiments, the first outer surface and secondouter surface comprise different geometries. In still other embodiments,the first outer surface and second outer surface geometry are generallyspherical.

In some embodiments, only the first outer surface geometry is generallyspherical. In some embodiments, only the second outer surface geometryis generally flat with radiused edges. In others, the second outersurface geometry is generally flat near the center, transitioning togenerally spherical near the radial edges. Still further, in someembodiments, the second outer surface geometry is generally flat andtransitioning to a proportionately large spherical radius, to replicatea worn or surgically prepared endplate surface.

In any one of the embodiments, the first inner surface and the secondinner surface are flat surfaces. In any one of the embodiments, thefirst inner surface and the second inner surface are concave surfaces.Still further, in any one of the embodiments, the first inner surfaceand the second inner surface are convex surfaces. Further still, in anyone of the embodiments, the first inner surface and the second innersurface are non-flat surfaces.

In any of the aforementioned embodiments, the first inner surface andthe second inner surface are textured surfaces, wherein the texturedsurface is surface configured to receive a fixation compound intended tobond an intermediate core to the implant.

In any one of the embodiments, the intermediate core is configured to beshock-absorbing and biocompatible. In some embodiments, the intermediatecore is a hydrogel. In some embodiments, the intermediate core is apolymer.

In any one of the embodiments, the intermediate core upper surface isbonded to the first inner surface and the intermediate core lowersurface is bonded the second inner surface, and the bond is permanent.

In any one of the embodiments, the first inner surface and the secondinner surface are essentially parallel to each other about a centraltransverse plane.

In any one of the embodiments, the first endcap and second endcap arecentered about a central axis. In addition, some embodiments furthercomprise the at least one protrusion centered about the central axis. Instill other embodiments, the at least one protrusion is locatedoff-center from the central axis.

In some embodiments, the first outer surface and second outer surfacecomprise slightly increasing arcuate radii of curvature from the outerradial edge surface to a zone near the central axis. Additionally, insome embodiments the first outer surface and second outer surface areinclined to each other about a central transverse plane to replicate thelordotic angle of the disc space. Alternately, in some embodiments, thesuperior and inferior surface of the intermediate core are inclinedtoward each other about a central transverse axis to replicate thelordotic angle. In still other embodiments, the arcuate radii ofcurvature of the first and second outer surfaces are essentially mirrorimages about a central transverse plane.

In some embodiments, the planar configuration of the implant is circularin shape about the central axis. In some embodiments, the planarconfiguration of the implant is elliptical in shape about the centralaxis. In still other embodiments, the planar configuration of theimplant is a polygon in shape about the central axis. In some polygonconfigurations, the polygon comprises at least three edges, andpreferable four or more side edges. In some embodiments the side edgesare straight. In some polygon configurations, the polygon comprises anirregular polygon embodiment, wherein the side edges are curved, as in aReuleaux polygon. In other irregular embodiments, the side edges aredifferent lengths. In still other irregular polygon embodiments, theimplant configuration may comprise any combination of number of sides,straight or curved edges and or length of individual edges.

In some embodiments, the implant comprises an anterior-posteriordimension that is greater than the overall arcuate height of theimplant, wherein the ratio of the anterior-posterior dimension to theoverall arcuate height is at least 1.01:1. In other embodiments, theratio of the anterior-posterior dimension to the overall arcuate heightis at least 1.1:1. In still other embodiments, the ratio of theanterior-posterior dimension to the overall arcuate height is at least1.2:1. In still other embodiments, the ratio of the anterior-posteriordimension to the overall arcuate height is at least 1.5:1; or at least2.0:1.

In some embodiments, the implant comprises a medial-lateral dimensionthat is greater than the overall arcuate height of the implant, whereinthe ratio of the medial-lateral dimension to the overall arcuate heightis at least 1.01:1. In other embodiments, the ratio of themedial-lateral dimension to the overall arcuate height is at least1.1:1. In still other embodiments, the ratio of the medial-lateraldimension to the overall arcuate height is at least 1.2:1. In stillother embodiments, the ratio of the medial-lateral dimension to theoverall arcuate height is at least 1.5:1; at least 2.0:1, 3.0:1, or4.0:1.

In some embodiments the implant comprises at least two protrusions. Inother embodiments, the implant comprises exactly two protrusions. Insome embodiments, the protrusions will be on different bearing surfaces.In other embodiments the protrusions will be on the same bearingsurface. In some embodiments, the implant will have at least twoprotrusions on one bearing surface and at least one protrusion onanother bearing surface.

In some embodiments, the implant comprises at least one conic protrusionon at least one bearing surface. In a preferred embodiment, the bearingsurface will be an articulating surface.

Still further embodiments of the implant comprise two endcap bearingsurfaces, the first endcap further comprises a first inner surface, andthe second endcap comprises a second inner surface. Still further, insome embodiments, the first inner surface and the second inner surfaceeach comprise a recessed cavity, thus creating a third inner surface(recessed area) and fourth inner surface (recessed area) on their innersurfaces respectively.

In matching configurations to the preceding embodiments, theintermediate core has a raised first surface and raised second surface,wherein the raised first surface of the intermediate core is configuredto mate within the recessed cavity of the third inner surface of thefirst endcap, and the raised second surface is configured to mate withinthe recessed cavity of the fourth inner surface of the second endcap.

Still further, in an alternate (mirror-type) embodiment, the first innersurface of the first endcap and the second inner surface of the secondendcap comprise a protruding third surface and fourth protruding surfacerespectively; wherein the intermediate core has a recessed cavity in thefirst surface and a recessed cavity is the second surface, and whereinthe recessed surface of the first surface of the intermediate core isconfigured to mate with the protruding third surface of the firstendcap, and the recessed cavity of the second surface of theintermediate core is configured to mate with the fourth raised surfaceof the second endcap.

In some embodiments, at least one of the first outer surface and thesecond outer surface is a bearing surface. Still further, in someembodiments, at least one of the first outer surface and the secondouter surface is a polished bearing surface, wherein the at least onepolished bearing surface has a surface finish ≤4 RMS. Further still, atleast one of the first outer surface and the second outer surface is anarticulating surface.

In some embodiments of the implant, exactly one of the bearing surfacesis an articulating surface and at least a portion of the oppositebearing surface is a textured surface. In some embodiments, at least aportion of one of the first bearing surface or second bearing surface istextured. In still other embodiments, at least a portion of both thefirst bearing surface and the second bearing surface is textured. Stillfurther, in some embodiments, both the first outer surface and thesecond outer surface is a non-articulating surface and comprises morethan one protrusion. In some of the preceding embodiments, the texturedsurface comprises more than one protrusion configured to contact aportion of at least one adjacent vertebral endplate.

In some of the preceding embodiments, at least a portion of the firstouter surface or the second outer surface comprises a surface finish≥125 RMS. In some embodiments, a surface comprising a surface finish≥125 RMS is a textured surface. In some embodiments, a textured surfaceis a surface configured to receive a fixation compound. In someembodiments, a textured surface comprises a porous structure or porouscoating, intended to mimic cancellous bone and to promote bone ingrowth.

In any one of the preceding embodiments, the implant is configured foruse in the spine of a human, wherein the implant is a spinal discimplant.

In any one of the preceding embodiments, the implant is configured foruse in the spine of a human, wherein the implant is a spinal fusionimplant.

In any one of the preceding embodiments, the implant is configured foruse in the spine of a human, wherein the implant comprises anarticulating surface on one side and a fusion surface on the oppositeside.

In any one of the preceding embodiments, the implant comprises acircular configuration in a transverse (horizontal) plane. Support forthe amendment can be found in original claim 13 and Paras. 00169, 00225and 00243, at least.

In any one of the preceding embodiments, the implant is a unitary discimplant comprising no independent moving components.

In some of the preceding embodiments, the implant is a unitary discimplant comprising no independent moving components, as assembled.

In some embodiments, the implant described herein may be used in ajoint, other than in the spine (of a human). In some embodiments, theimplant is configured for use in an articulating joint. In otherembodiments, the implant is configured for use in the spine of ananimal. In still further embodiments, the implant is configured for usein a robotic articulating joint. In still further embodiments, any oneof the preceding embodiments may be configured for (human) prosthetics.

Provided herein is another assembled implant adapted for placementbetween adjacent endplates of a vertebral joint comprising: a firstendcap having a first outer surface and first inner surface, a firstprotruding attachment means, and an outer radial edge; a second endcaphaving a second outer surface and second inner surface, a secondprotruding attachment means configured to mate with the first protrudingattachment means, and outer radial edge, an intermediate core having anupper surface and lower surface configured to mate between the firstinner surface and the second inner surface, and further comprising acentral opening configured to accommodate the first and secondprotruding attachments when assembled; at least one protrusion on atleast one endcap surface, wherein the at least one protrusion isconfigured to contact a portion of at least one adjacent vertebralendplate.

In some embodiments, the first protruding attachment means is aprotruding cylinder with a hole, centered about the central axis. Insome embodiments, the first protruding attachment means is a protrudingpolygon having three or more sides with a hole, centered about thecentral axis. In some embodiments, the hole is a polygon having three orsides. Still further, in some embodiments, the hole may be a blind holeor a tapered hole. In some embodiments, the tapered hole comprises aMorse taper.

In some embodiments, the second protruding attachment means is aprotruding cylinder with a hole, centered about the central axis. Insome embodiments, the second protruding attachment means is a protrudingpolygon with a hole, centered about the central axis. In someembodiments, the hole is polygonal. Still further, in some embodiments,the hole may be a blind hole or a tapered hole. In some embodiments, thetapered hole comprises a Morse taper.

Still further, in some embodiments, the first protruding attachmentmeans is a protruding cylinder, centered about the central axis. In someembodiments, the second protruding attachment means is a protrudingpolygon having three or more sides, centered about the central axis. Insome embodiments, the second protruding attachment means is a protrudingcylinder, centered about the central axis.

In some embodiments, the first outer surface is an articulating surface.In some embodiments, the second outer surface is an articulatingsurface. In still other embodiments, the first outer surface and secondouter surface geometries are the same. Still further, in otherembodiments, the first outer surface and second outer surface comprisedifferent geometries.

In some embodiments, the first outer surface and second outer surfacegeometry are generally convex. In other embodiments, the first outersurface and second outer surface geometry are generally spherical. Instill other embodiments, the first outer surface geometry is generallyspherical. Still further, in other embodiments, the first outer surfacegeometry is generally spherical to convex. Yet in other embodiments, thefirst outer surface geometry is generally convex to spherical.

In some embodiments, the second outer surface geometry is generallyflat. In other embodiments, the second outer surface geometry isgenerally flat to convex. Yet in other embodiments, the second outersurface geometry is generally flat and transitioning to aproportionately large spherical radius.

In some embodiments, the first inner surface and the second innersurface are flat surfaces. In some embodiments, the first inner surfaceand the second inner surface are concave surfaces. In some embodiments,the first inner surface and the second inner surface are convexsurfaces. In still other embodiments, the first inner surface and thesecond inner surface are non-flat surfaces. In any one of the precedingembodiments the first inner surface and the second inner surface aretextured surfaces. Still further, any one of textured surfaces is asurface configured to receive a fixation compound. Additionally, any oneof textured surfaces is a porous coated surface configured to mimiccancellous bone and promote ingrowth.

In some embodiments, the intermediate core is configured to beshock-absorbing. Further, the intermediate core is biocompatible.Further still, the intermediate core may be a hydrogel or a polymer.

In any one of the preceding configurations, the first surface of theintermediate core is bonded to the first inner surface of the firstendcap, and the second surface of the intermediate core is bonded thesecond inner surface of the second endcap. In any one of the precedingembodiments, the bond is permanent.

In some embodiments, the first outer surface and second outer surfaceare inclined to each other about a central transverse plane to replicatethe lordotic angle of the disc space. Alternately, in some embodiments,the superior and inferior surface of the intermediate core are inclinedtoward each other about a central transverse axis to replicate thelordotic angle. In still other embodiments, the arcuate radii ofcurvature of the first and second outer surfaces are essentially mirrorimages about a central transverse plane.

In some embodiments, the first endcap and second endcap are centeredabout a central axis. In some embodiments, at least one protrusion iscentered about the central axis. In some embodiments the at least oneprotrusion is located off-center from the central axis.

In still other embodiments, the first outer surface and second outersurface comprise slightly increasing arcuate radii of curvature from anouter radial edge surface to the central axis. Still further, in otherembodiments, the first outer surface and second outer surface areessentially mirror images to each other about a central transverseplane.

In any one of the preceding embodiments, the planar configuration of theimplant is circular in shape about the central axis. In any one of thepreceding embodiments, the planar configuration of the implant iselliptical in shape about the central axis. Still further, in any one ofthe preceding embodiments, the planar configuration of the implant ispolygonal in shape about the central axis, wherein the polygon comprisesat least three side edges, and preferably four side edges. In any one ofthe preceding embodiments, the planar configuration of the implantcomprises an irregular Reuleaux polygon. In any one of the precedingembodiments, the irregular Reuleaux polygon may comprise straight sideedges, curved side edges or combinations of straight and curved sideedges. Additionally, the lengths of the side edges need not be the samelength.

In some embodiments, the implant comprises an anterior-posteriordimension that is greater than the overall arcuate height of theimplant. In some embodiments, the ratio of the anterior-posteriordimension to the overall arcuate height is at least 1.01:1. In someembodiments, the ratio of the anterior-posterior dimension to theoverall arcuate height is at least 1.1:1. In still other embodiments,the ratio of the anterior-posterior dimension to the overall arcuateheight is at least 1.2:1. In still other embodiments, the ratio of theanterior-posterior dimension to the overall arcuate height is at least1.5:1, or at least 2.0:1.

In some embodiments, the implant comprises a medial-lateral dimensionthat is greater than the overall arcuate height of the implant. In someembodiments, the ratio of the medial-lateral dimension to the overallarcuate height is at least 1.01:1. In other embodiments, the ratio ofthe medial-lateral dimension to the overall arcuate height is at least1.1:1. In still other embodiments, the ratio of the medial-lateraldimension to the overall arcuate height is at least 1.2:1. In stillother embodiments, the ratio of the medial-lateral dimension to theoverall arcuate height is at least 1.5:1; at least 2.0:1, at least3.0:1, or at least 4.0:1.

In some embodiments, the implant comprises at least two protrusions. Insome embodiments, the implant comprises exactly two protrusions. Instill other embodiments, the implant comprises at least one conicprotrusion on at least one outer bearing surface. In some embodiments,at least one of the first outer surface and the second outer surface isan articulating bearing surface. In some embodiments, at least one ofthe first outer surface and the second outer surface is a polishedarticulating bearing surface. In some embodiments, the at least onepolished articulating bearing surface has a surface finish ≤4 RMS.

In some embodiments, exactly one of the bearing surfaces is anarticulating surface and at least a portion of the other of the surfacesis a textured surface. In some embodiments, at least a portion of atleast one of the first outer surface and the second outer surface istextured. In some embodiments, at least a portion of both of the firstouter surface and the second outer surface is textured. In still otherembodiments, both of the first outer surface and the second outersurface is a non-articulating surface. Still further, in someembodiments, at least a portion of both of the first outer surface andthe second outer surface is a fusion surface. In any one of thepreceding embodiments, the textured, non-articulating or fusion surfacemay comprise more than one protrusion configured to contact a portion ofat least one adjacent vertebral endplate. In any one of the precedingembodiments, the textured, non-articulating or fusion surface comprisesa surface finish ≥125 RMS. In any one of the preceding embodiments, atextured surface is a surface configured to receive a fixation compound.In some embodiments, a textured surface comprises a porous structure orporous coating, intended to mimic cancellous bone and to promote boneingrowth.

In any one of the preceding embodiments, the implant is configured foruse in the spine of a human, wherein the implant is a spinal discimplant.

In any one of the preceding embodiments, the implant is configured foruse in the spine of a human, wherein the implant is a spinal fusionimplant.

In any one of the preceding embodiments, the implant is configured foruse in the spine of a human, wherein the implant comprises anarticulating surface on one side and a fusion surface on the oppositeside.

In any one of the preceding embodiments, the implant is a unitary discimplant comprising no independent moving components.

In some of the preceding embodiments, the implant is a unitary discimplant comprising no independent moving components, as assembled.

In some embodiments, the implant described herein may be used in ajoint, other than in the spine. In some embodiments, the implant isconfigured for use in an articulating joint. In other embodiments, theimplant is configured for use in the spine of an animal. In stillfurther embodiments, the implant is configured for use in a roboticarticulating joint. In still further embodiments, any one of thepreceding embodiments may be configured for prosthetics.

Provided herein is a unitary implant comprising at least one tether,configured for placement in the void of a conic feature. In otherembodiments the implant further comprises at least one tether configuredfor placement in at least one fenestration.

In either of the immediately preceding configurations, the tethercomprises at least one of:

autologous tissue; allograft tissue; xenograft tissue; synthetic graftmaterial; stem cells, chondrocytes; proteins; and/or growth promotingfactors.

In still other configurations, the implant may further comprise anabutment on the second outer surface to restrict motion between theimplant and the joint surface. In some embodiments, the abutment maycomprise: a keel; a fin; a raised ridge; a post; or a spike. In stillother embodiments the implant may comprise more than one abutment. Instill other embodiments, the more than one abutment may be located onmore than one bearing surface.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIGS. 1 & 2 are representative side and isometric views of adiscus-shaped, unitary implant having penetrating protrusions about thecentral axis.

FIG. 3 is a representative cross-sectional view of a discus-shaped,unitary implant comprising penetrating protrusions about the centralaxis, illustrating penetration of cartilage and or bony endplates ofadjacent vertebral bodies.

FIGS. 4 & 5 are representative top (plan) and side views of thediscus-shaped, unitary implant of FIG. 1, illustrating variable heightoptions as measured about the arcuate height of the implant.

FIGS. 6 & 7 are representative top (plan) and side views of anelliptically shaped unitary discus implant having penetratingprotrusions about the central axis on both surfaces, illustratingvariable height options as measured about the arcuate height of theimplant.

FIGS. 8 & 9 are representative top (plan) and side views, of anirregular polygon-shaped unitary implant, approximating the vertebralperimeter and having penetrating protrusions about the central axis,illustrating variable height options as measured about the arcuateheight of the implant.

FIGS. 10 & 11 are top and side views of a representative variant of FIG.4, illustrating variable lordosis (or kyphosis) of arcuate surfaces thatare inclined relative to each other about a central Transverse plane,and represented by variable heights measured from the anterior andposterior sides of the implant.

FIGS. 12 & 13 are top and side views of a representative irregularpolygon shaped implant illustrating variable lordosis (or kyphosis) ofarcuate surfaces that are inclined relative to each other about acentral Transverse plane, and represented by variable heights measuredfrom the anterior and posterior sides of the implant.

FIG. 14 is a side profile view of a discus-shaped, unitary implantvariation, similar to that depicted in FIG. 1, comprising a penetratingprotrusions about the central axis on just one surface.

FIG. 15 is an isometric view of the implant shown in FIG. 14illustrating an embodiment with a smooth bearing surface.

FIGS. 16-18 are representative top, cross-section and ISO views of animplant comprising a truncated conic protrusion on both surfaces, have awider girth, and comprising a thru-hole, located on or about the centralaxis of the implant.

FIGS. 19-21 are representative top, cross-section and ISO views of animplant similar to one depicted in FIGS. 16-18, comprising a truncatedconic protrusion on only one surface, have a wider girth, and comprisinga blind hole, located on or about the central axis of the implant, whichextends into the body of the implant but does not break through theopposite surface.

FIGS. 22-24 are representative top, cross-section and ISO views of animplant similar to one depicted in FIGS. 16-18 and comprising abiocompatible tether or wick-tethering device.

FIGS. 25-27 are representative top, cross-section and side views of animplant similar to one depicted in FIGS. 19-21 and comprising abiocompatible tether or wick-tethering device.

FIGS. 28-30 are representative side, bottom and ISO views of adiscus-shaped, unitary implant having a single penetrating protrusionabout the central axis on one surface and multiple protrusions on theopposite surface.

FIGS. 31-33 are representative side, bottom and isometric views of adiscus-shaped, unitary implant having multiple penetrating protrusion onone surface and no protrusions on the opposite surface.

FIGS. 34-36 are representative isometric views of the implant similar toFIG. 33 illustrating alternate configurations comprising articulating,non-articulating and textured/fusion bearing surface combinations.

FIGS. 37-39 are representative section, plan and isometric views of adiscus-shaped, unitary implant comprising a truncated conic protrusionabout the central axis, with an optionally concentric centralblind-hole. In addition, multiple anti-rotation protrusions are locatedon the same surface. FIGS. 40-43 are representative A/P, side, bottomand isometric views of an irregular polygon-shaped (i.e.: Reuleauxpolygon) unitary implant with a vertebral-approximating perimeter,comprising an elongated protruding rib or fin on one surface and asmooth opposite surface with no protrusions. The protruding fin is analternative anti-rotation feature, preventing relative motion betweenthe implant and the adjacent vertebral body.

FIGS. 44-47 are representative isometric views of FIG. 43 comprisingalternative configurations of textured surfaces.

FIGS. 48-51 are representative plan, cross-section, ISO and explodedviews of a discus-shaped, assembled unitary implant comprising anintermediate shock-absorbing core permanently bonded between the upperand lower discus-shaped endcap components.

FIGS. 52-55 are representative plan, cross-section, ISO and explodedviews of a discus-shaped, assembled unitary implant comprising recessesin the implant end caps, with corresponding protruding sections on theintermediate shock absorbing core, permanently bonded between the upperand lower discus-shaped endcap components

FIGS. 56-59 are representative plan, cross-section, ISO and explodedviews of a discus-shaped, assembled unitary implant comprising end capswhich employ a sliding fit mechanism to allow compressive axialmovement, yet prevent lateral movement of one end cap relative to theother end cap. The shock absorbing core has a central through-hole. Thesurfaces of the shock absorbing core are permanently bonded toadjacently mating surfaces of the end caps.

FIGS. 60-62 are representative ISO views of salvage/fusion devices,comprising textured or bone-ingrowth promoting surfaces on both bearingendplate surfaces.

FIG. 63 is a representative isometric view of a Reuleaux-shaped,assembled unitary implant comprising an intermediate shock-absorbingcore permanently bonded between the upper and lower endcap components.

FIGS. 64 and 65 are representative ISO views of additionalsalvage/fusion devices, comprising textured or bone-ingrowth promotingand/or articulating surfaces on the bearing endplate surfaces.

These representative views are not intended as limiting representations.One skilled in the art would recognize that this implant could befabricated in a wide variety of combination and configurations asillustrated herein, or from any number of recognized implantablematerials, bone-ingrowth promoting surfaces, textures or coatings, or beconfigured similarly to any of the previously described shapes orconfigurations.

DETAILED DESCRIPTION OF THE INVENTION

The typical joint comprises two (and sometime three or more) mating boneend surfaces that are in close proximity or direct contact, each usuallycovered by and separated by a layer of hyaline cartilage and typicallylubricated by natural joint synovial fluids. Structural classificationnames and divides joints according to the type of binding tissue thatconnects the bones to each other. There are three structuralclassifications of joints: fibrous joint—joined by dense regularconnective tissue that is rich in collagen fibers: cartilaginousjoint—joined by cartilage: and synovial joint—not directly joined—thebones have a synovial cavity and are united by the dense irregularconnective tissue that forms the articular capsule that is normallyassociated with accessory ligaments.

Further, joints can also be classified functionally according to thetype and degree of movement they allow; for example:Synarthrosis—permits little or no mobility. Most synarthrosis joints arefibrous joints (e.g., skull sutures): Amphiarthrosis—permits slightmobility. Most amphiarthrosis joints are cartilaginous joints (e.g.,intervertebral discs): Diarthrosis—freely movable. All diarthrosisjoints are synovial joints (e.g., shoulder, hip, elbow, knee, etc.), andthe terms “diarthrosis” and “synovial joint” are considered equivalentby Terminologia Anatomica.

Diarthroses can in turn be classified into six groups according to thetype of movement they allow: arthrodia, enarthrosis, ginglymus, rotarydiarthrosis, condyloid articulation and articulation by reciprocalreception.

Joints can also be classified according to the number of axes ofmovement they allow, into mono-axial, biaxial and multi-axial. Stillanother classification is according to the degrees of freedom allowed,and distinguished between joints with one, two or three degrees offreedom. A further classification is according to the number and shapesof the articular surfaces: flat, concave and convex surfaces.

Joints can also be classified based on their anatomy or on theirbiomechanical properties. According to the anatomic classification,joints are subdivided into simple and compound, depending on the numberof bones involved, and into complex and combination joints: SimpleJoint: 2 articulation surfaces (e.g. shoulder joint, hip joint):Compound Joint: 3 or more articulation surfaces (e.g. radiocarpaljoint), and: Complex Joint: 2 or more articulation surfaces and anarticular disc or meniscus (e.g. knee joint).

Still further, the joints may be classified anatomically into thefollowing groups: Articulations of hand; Elbow joints; Wrist joints;Axillary articulations; Sternoclavicular joints; Vertebralarticulations; Temporomandibular joints; Sacroiliac joints; Hip joints;Knee joints; and Articulations of foot.

As defined herein, the term “unitary” shall mean, either an individual,single-component implant, or an implant comprised of more than onecomponent, but having no internal moving parts or components, asassembled, wherein the implant performs as a single unit, or behaves asa single component. The intent of this description is to clarify thatthe implant component, or assembled components of this implant are notlikely to generate intra-articular wear debris of its own making, orfrom its own core components, as a result of intra-component abrasion.

As defined herein, the term “adjacent joint surface” shall mean either,the naturally occurring state, or surgically prepared joint surfacewhich is immediately adjacent to the surgically implanted device.

Provided herein is a unitary intervertebral device, comprising noindependent moving components, for non-fusion articulation applications.The interbody articulating device allows for limited flexion androtation between adjacent vertebrae, helping to preserve or restorenear-normal motion between adjacent vertebrae. Rotational motion isachieved through one or more protrusions incorporated into the spinalinterbody device. In one articulating form, a first protrusion extendsperpendicularly from the superior aspect of the discus-shape of theinterbody device forming a spike or rotational cone protrusion, while asecond protrusion extends axially from the inferior aspect of theinterbody device to form a second spike or rotational cone protrusion.In some embodiments, protrusions preferably extend perpendicularly fromthe apex of both the first and second arcuate articulating surfacesabout the central axis. In another form, a single protrusion extendsperpendicularly from the superior (first) aspect of a circular-shape ofthe interbody device to form a spike or anchoring protrusion, while theinferior (second) surface is slightly rounded and smooth. Alternately,the inferior surface comprises a textured or bone-ingrowth promotingsurface. One or both of the first and/or second arcuate surfaces may behighly polished. Numerous planar geometries are described to definevarious profiles of the disc replacement implant which may be utilized,including irregular Reuleaux polygons. Numerous variations of the discreplacement are described. Similarly configured fusion salvage devicesare also described.

In some embodiments, the implant is a joint implant, having applicationsin artificial limbs, robotics, or other joints and mechanisms. In someembodiments, the implant is a medical implant having applications forveterinary applications intended to repair or replace a joint in ananimal. In still other preferred embodiments, the implant is a humanmedical implant intended for a complex cartilaginous joint of the spine(intervertebral disc).

Provided herein is a unitary implant adapted for placement betweenadjacent surfaces of a joint comprising: a first bearing surface and asecond bearing surface, wherein the first and second bearing surfacesare generally convex and configured to have bearing surface curvaturethat generally conforms to the concave geometry of the adjacent jointsurfaces; an outer radial edge surface; and a first protrusion on thefirst bearing surface, as illustrated in FIG. 14 or 15, wherein thefirst protrusion is configured to contact a central portion of a firstadjacent joint surface, and wherein the first protrusion is adapted toallow rotation about an axis.

As defined herein, convex shall be construed to mean: having an outlineor surface curved like the exterior of a circle or sphere.

In some embodiments, the unitary implant further comprises a secondprotrusion on the second bearing surface, as illustrated in any one ofFIG. 1-3, 5, 7, 9, 11, or 13, wherein the second protrusion isconfigured to contact a central portion of a second adjacent surface,and wherein the second protrusion is adapted to allow rotation about thecommon axis of the first and second protrusions.

In some embodiments of the unitary implant the first protrusion isconical. In some embodiments, the second protrusion is conical. In stillother embodiments, the first protrusion or second protrusion maycomprise a cone, a curved cone (sometimes referred to as parabolic orhyperbolic cones), a truncated cone, or a cylinder. In other words, theprotrusion may comprise any appropriate shape that would facilitaterotation, when placed about a central, rotational axis. In someembodiments, the protrusions are different on opposite surfaces. Asillustrated in FIG. 3, the protrusions would intentionally penetrate theexisting (or remaining) cartilage on the adjacent endplates of a joint,and at least minimally penetrate the boney endplate at or about theapproximate center of rotation of the joint to stabilize the implant.

Accordingly, an illustrative intervertebral disc prosthesis 10 asrepresented by FIGS. 1-3 is a unitary (single component), symmetric,discus-shaped device having highly polished, gradually curving superiorand inferior surfaces 11 and 12 with slightly increasing arcuategeometry from the peripheral blended edges 16 and 17 to the central axisW, culminating in protrusions 13 and 14 about the central axis on boththe superior 11 and inferior 12 surfaces. The sidewalls of the discimplant 15 transition smoothly with blended edges 16 and 17.

The terms “superior” and “inferior” are used herein with reference tothe orientation of the disc 10 when it is implanted in the human bodywherein the head is superior to the feet and the feet are inferior tothe head on an erect spine of the human body. Other paired terms havingsimilar meaning in this specification include; “upper” or “cephalad”,(meaning toward the head); and “lower” and “caudal” or “caudad” (meaningtoward the tail or feet, and away from the head).

The protrusions 13 and 14 extending from the superior 11 and inferior 12surfaces respectively, engage the adjacent cephalad 18 and caudal 19vertebra respectively, piercing any remaining cartilage on the endplates20 and 21 in the approximate central region of their respective bearingsurfaces, to retain the disc prosthesis in position between the vertebraas shown in FIG. 3. Advantageously, any remaining cartilage on theendplates 20 and 21 would be beneficial to the highly polishedsurface(s) and protrusion(s), promoting improved rotational propertiesfor the implant about the protrusions. Additionally, over time, anyminor variations between the cartilage bearing surfaces would naturallyconform to the approximately similar radial geometry of the implantbearing surfaces, minimizing or completely eliminating the need tosurgically prepare the endplate surface to match the implant.

The penetrating protrusions 13 or 14 can be any surface of revolutionabout the central axis W where the base is broader than the tip. Theacute end of the tip protrusion may be pointed or slightly rounded.Similarly, the protrusion may have a base of any geometry projected tothe tip or apex of any geometry as long as it is smaller than the base.Preferably, in this configuration, the protrusion would be configured topromote rotation about the central axis W, meaning, the protrusion(s)would be circular in nature having a single axis of rotation.

The penetrating protrusion tips 13 and 14 would intentionally penetrate,at least minimally, into the approximate articulating center of thesuperior and inferior cartilaginous covered endplates 20 and 21, ordebrided bony endplates, as illustrated in FIG. 3. The penetratingprotrusion would have the purpose of providing a pseudo anchor, orspatial immobilizing member for the device, to position and preventmigration or expulsion of the implant during flexion/extension of thevertebral column. Additionally, in the case where the penetratingprotrusions comprise a singular axis of revolution on the articulatingsurface of the implant, they would also serve as the axis of rotationbetween the implant and the adjacent vertebral body. Height of theprotrusions can typically range from 0.3 mm to 2.5 mm.

The penetrating protrusions may also act as microfracture point(s) forthe vertebral endplates. There is significant documentation in theliterature that demonstrates how the human vertebral endplates will tendto calcify resulting in the early stages of disc degeneration, as earlyas age 25.

The vertebral endplates are identifiable from an early embryologicalstage, and have an osseous as well as a hyaline cartilage component. Thecartilaginous component generates interest since it persists throughoutnormal maturation while the adjacent vertebrae undergo ossification. Itcomprises a gel of hydrated proteoglycan molecules reinforced by anetwork of collagen fibrils. Unlike the articular cartilage of thesynovial joints, the collagen fibrils do not connect the endplatedirectly to the vertebral bone, although the endplate does have intimatecontact with the disc through the lamellae of the inner annulus. Anetwork of microscopic blood vessels penetrates the endplates duringdevelopment of the growing spine, principally to provide nutrition forthe disc, before disappearing around the time of skeletal maturity(i.e.: ossification). Apart from a sparse vascular supply in the outerlamellae of the annulus, mature discs are almost totally reliant ondiffusion of essential solutes across the endplates for nutrition andmetabolic exchange. Once ossification of the endplates occurs, nofurther direct nutrition is received by the endplate cartilage from thevertebral marrow, limiting its ability for self-repair.

Proteoglycan molecules within the matrix are critical for the control ofsolute transport and maintenance of water content in particularthroughout the disc, and depletion of proteoglycans from the endplatecartilage is associated with loss of proteoglycans from the nucleus. Itfollows therefore that proteoglycan loss would ultimately lead todegeneration of the disc and endplate cartilage. Upon reaching skeletalmaturity the cartilage of the endplate undergoes substantial remodeling,resulting in extensive mineralization which is eventually resorbed andreplaced by true bone. Importantly, this new tissue most likely impedesthe hitherto critical diffusion and nutrient exchange between thevertebral marrow, endplate cartilage and the disc. The small bloodvessels within the endplate likewise become obliterated by thiscalcification, further limiting the exchange of vital nutrients.

Perhaps surprisingly, the endplate can become re-vascularized aftermaturity in some species under normal and pathological conditions. In atleast one sheep study, the re-vascularization, presumed to be an attemptat tissue repair, was not able to reverse the inevitable cascade ofdegeneration caused by annular disruption. However, the creation ofblood vessels in the endplate occurred by activation of the matrixdegrading metalloproteinase (MMP) enzymes which are normally maintainedin a latent form by tissue inhibitors.

The human spine may have similar regenerative potential to repair, or atleast lubricate the cartilaginous endplate near the protruding point offixation 13, 14 for the artificial disc, in a manner similar to the endsof long bones with synovial joints as has been previously demonstratedby micro-fracturing techniques. Specifically, in addition to providing arotation anchor, the penetrating protrusion tip(s) would cause theequivalent of a microfracture to the vertebral endplate resulting in anatural repair response from the vertebra in the form of vascularmicro-vessels forming in and around the penetration point. Themicro-vessels would provide a means for supplying regenerative bloodsupply and nutrients from the vertebral marrow through the otherwisecalcified endplate structure of the vertebral body to the cartilage.Alterations in the ossified endplates, due to the microfracture effectsof the penetrating protrusions would provide a renewed source of blood,stem cells and nutrients from the vertebral bodies and would likelyresult in reformation of a pseudo-cartilage or fibrocartilage around theprotrusions.

As has been shown in the human knee, this natural response frommicrofracture will frequently lead to the formation of cartilage-likerepair tissue, sometimes referred to as fibro-cartilage, often with amixture of hyaline cartilage formed within and around the periphery ofthe fibrocartilage. Although not as strong or durable as hyalinecartilage, the fibrocartilage still provides a better cushion andarticulation surface than bone itself. When this fibrocartilage responseis duplicated around the penetrating protrusions tip(s) of the discussimplant, it will serve as a bridging material between the endplate, andthe remaining native cartilage on the endplate, providing an excellentarticulating area for the implant.

Still further, the first protrusion or second protrusion may comprise atruncated cone with a hole about the central axis, or a cylinder with ahole about the central axis. Still further, the hole in the protrusionmay be a blind hole or a thru-hole that penetrates through the entireimplant, as illustrated in FIGS. 16-21.

In some embodiments, the implant comprises a truncated cone with a holeabout the central axis, or a cylinder with a hole about the centralaxis, the implant may also comprise a tethering feature that isconfigured to promote ingrowth or attachment to the adjacent vertebra,as illustrated in FIGS. 22-27. In some embodiments, the attachment maybe to just one adjacent endplate or vertebra. In other configurations,the attachment may be to both of the adjacent endplates or vertebrae.Such a tethered configuration would provide for a unique implant designthat would promote a new form of pseudo-ligamentous fixation between theadjacent vertebrae, having either polished, articular bearing surfaces,fusion surfaces, or both. In the case where there is an articularbearing surface coupled with a tether, the combined interface wouldpotentially allow for limited rotation, where the tether would act as asubstitute for native spinal ligamentous tissues.

In some embodiments, the first protrusion and/or the second protrusionis adapted to penetrate at least the cartilage of the first adjacentjoint surface and/or the second adjacent surface providing an extremelyconservative surgical procedure. As illustrated by FIGS. 1-13, nospecial articular endplate preparation would be required to insert theimplant and obtain cartilage and/or at last partial endplate penetrationwith the protrusion(s). In other embodiments, a first protrusion only isadapted to penetrate the endplate of a first adjacent joint surfaceonly, as illustrated by FIGS. 14 and 15.

In other embodiments of the unitary implant, the implant may comprisinga polished first bearing surface, with no protrusions, and further maycomprise at least a first and second (or more protrusions) on the secondbearing surface as illustrated in FIGS. 31-35, wherein the at leastfirst and second protrusion are configured to contact a portion of asecond adjacent surface, preferably penetrating at least a portion ofthe adjacent endplate, and wherein the at least first and secondprotrusion are adapted to prevent movement between the second bearingsurface and the second adjacent surface. Alternately, this configurationmay also comprise a textured surface in addition to the protrusions, tofurther promote boney or fibro-cartilage attachment between the implantand the adjacent endplate, as illustrated in FIG. 36.

In still other embodiments of the unitary implant comprising a firstprotrusion on the first bearing surface, the implant may comprise atleast a second and third protrusion on the second bearing surface asillustrated in FIGS. 28-30, wherein the at least second and thirdprotrusion are configured to contact a portion of a second adjacentsurface, preferably penetrating at least a portion of the adjacentendplate, and wherein the at least second and third protrusion areadapted to prevent movement between the second bearing surface and thesecond adjacent surface.

In some embodiments of the unitary implant, the implant is generallycircular in shape 10 about a central axis (i.e.: FIG. 4) comprising acircular perimeter 22. In other embodiments, the implant isnon-circular, polygonal or irregular polygonal in shape, 30, 40 about acentral axis. In certain preferred embodiments, the implant comprises anelliptical planar shape or a common variant thereof. Variousnon-limiting illustrations of such configurations are illustrated inFIGS. 4, 6 and 8.

As defined herein, “elliptical” shall mean a curve on a planesurrounding two focal points such that a straight line drawn from one ofthe focal points to any point on the curve and then back to the otherfocal point has the same length for every point on the curve. As such,it is a generalization of a circle which is a special type of an ellipsethat has both focal points at the same location, as illustrated by thenon-limiting example of FIG. 6 having an elliptical perimeter 31. Theshape of an ellipse is represented by its eccentricity which for anellipse can be any number from 0, (the limiting case of a circle), toarbitrarily close to, but less than 1. Alternatively, the ellipticalshape may be defined as an irregular ellipse, wherein curve on a planesurrounding two focal points such that a straight line drawn from one ofthe focal points to any point on the curve and then back to the otherfocal point has the similar, but variable lengths for every point on thecurve.

Still further, in other preferred embodiments, the implant shape mayresemble a Reuleaux polygon planar shape comprising three or more sides.The Reuleaux polygon shape 40 may be in the form of an irregularpolygon, wherein at least one or more sides of the polygon are straight,or wherein at least one side has a different length than the remainingsides. Still further the Reuleaux polygon shape may be in the form of anirregular Reuleaux polygon, wherein at least one or more sides of thepolygon are curved 41, or wherein at least one (curved) side has adifferent length than the remaining sides, as illustrated by thenon-limiting examples of FIGS. 8, 12, and 40-47. Still further theReuleaux polygon shape may have a combination of straight and curvedsides.

In some embodiments, the implant comprises an anatomic-like bearingsurface, wherein the curvature of the first bearing surface 11, 33, 43and the second bearing surface 12, 34, 44 is generally spherical or nearspherical. The geometry of these bearing surfaces can either be asurface of revolution about a center axis W, as represented by surfaces11 and 12 in implant 10; or they can be any swept surface as representby surfaces 33, 34, 43 and 44 in implants 30 and 40 or a lofted surface.A swept surface is defined as the geometry resulting from a sectionalcurve following a path of another curve. A lofted surface is defined asthe surface geometry formed by a matrix of varying section curves in onedirection along with varying section curves in another direction wherethe direction of the two sets of curves are different from each other.Typically, the direction of the curves are normal to each other, but donot need to be.

In other embodiments, the curvature of the first bearing surface and thesecond bearing surface is generally multi-radial in order to moreclosely match the native or prepared endplate surface. In still otherembodiments, the first bearing surface and the second bearing surfacegeometries are the same. Alternatively, in other embodiments, the firstbearing surface and the second bearing surface comprise differentgeometries.

Still further, in some embodiments the first bearing surface and thesecond bearing surface are mirrored, or symmetrical about a centraltransverse plane, wherein the overall arcuate height 23, 32, and 43 isconstant, as illustrated in the non-limiting examples of FIGS. 5, 7 and9.

In other embodiments, the first bearing surface and the second bearingsurface are inclined to each other about a central transverse plane tobetter match or reconstruct the natural curvature or lordosis andkyphosis of the spine, as illustrated in the non-limiting examples ofFIGS. 11 and 13.

In cervical and lumbar applications, the angle of inclination of thesuperior surface relative to the inferior surface is commonly referredto as the lordotic angle, and typically ranges between 0.1 and 20degrees, or more particularly between 4 and 15 degrees. (However, insome cases this angle may be as high as 25 degrees). As illustrated inFIG. 13, the lordotic angle 47 is such that the height on the anteriorsurface 45 is almost always greater than the posterior surface 46. Asfurther illustrated by FIG. 11, the lordosis or inclination anglebetween the first and second bearing surfaces may also be directlyimplied by describing an implant with different anterior 24 andposterior 25 dimensions. In the thoracic spine, the angle of inclinationis referred to as a kyphotic angle, the opposite of lordosis.

In some embodiments of the implant, the first bearing surface and thefirst protrusion are polished articulating surfaces as illustrated inthe non-limiting examples of FIGS. 28 and 29. In other embodiments, thesecond bearing surface and the second protrusion are polishedarticulating surfaces as illustrated in the non-limiting examples ofFIGS. 14 and 15. In this embodiment 50, the central protrusion 51,resides on only one surface of the implant verses protrusions 13 and 14on both surfaces (FIG. 11). Typically this protrusion would be on theinferior surface. However, it could also be located on the superiorsurface. The surface 52 opposite the surface with the protrusion 51 issufficiently smooth and polished in order to articulate against thenative cartilage or endplate, while minimizing wear. This embodiment ofone central protrusion on either the inferior or superior surface, butnot both, can be incorporated with any of the previously mentionedperimeter geometries (22, 31 and 41) with superior and inferior surfacespositioned either approximately parallel to each other (FIG. 11) whenviewed perpendicular to the coronal plane or at a lordotic angle 47,(FIG. 13).

In still others, all of the bearing surfaces and protrusions arepolished articulating surfaces, as illustrated in the non-limitingexamples of FIGS. 1-13.

In any one of the embodiments described herein, the first bearingsurface or second bearing surface may comprise or be manufactured fromat least one of the following materials: pyrolytic carbon, titanium,titanium nitride, tantalum, cobalt, chromium, polyethylene, PEEK®(Polyether ether ketone), Delrin®, alumina, zirconia, silicon carbide,silicon nitride, stainless steel, diamond, or a diamond like material.In some embodiments, the unitary implant may comprise a core fabricatedfrom one material having one set of properties, and an outer bearingsurface fabricated from another material having a different set ofproperties. As a non-limiting example, a pyrolytic carbon implant mayhave a graphite core and a pyrolytic carbon exterior for bearingsurfaces. Alternatively, an implant may have a first bearing surfacewith one set of material properties (i.e. low abrasion articulatingsurface), and a second bearing surface comprising different materialproperties (i.e.: fixation promoting surface), and an intermediate corecomprising yet a third set of material properties (dampening,shock-absorbing properties).

Provided herein is a unitary disc implant adapted for placement betweenadjacent vertebral surfaces of a spinal joint comprising: a firstbearing surface and a second bearing surface, wherein the first andsecond bearing surfaces are generally convex and configured to havecurvature that generally conforms to the concave geometry of theadjacent spinal joint surfaces; an outer radial edge surface; a firstprotrusion on the first bearing surface, wherein the first protrusion isconfigured to contact a central portion of a first adjacent spinal jointsurface, a second protrusion on the second bearing surface, wherein thesecond protrusion is configured to contact a central portion of a secondadjacent spinal surface, wherein the first protrusion and secondprotrusion are adapted to allow rotation about an axis, as illustratedin FIGS. 1-13, 16-18 and 48-58.

Provided herein is a unitary spinal disc implant adapted for placementbetween adjacent vertebral endplates comprising: a first bearing surfaceand an second bearing surface, wherein the first and second bearingsurfaces are generally convex and configured to have a sphericalcurvature geometry that conforms to the concave geometry of adjacentendplate surfaces; an outer radial edge surface that blends into thefirst and the second bearing surfaces; a conic protrusion on at leastone bearing surface for penetrating at least one of the adjacentendplates, wherein the conic protrusion is configured to contact acentral portion of at least one adjacent vertebral endplate, asillustrated in FIGS. 14, 15, and 19-21.

In some embodiments, the first bearing surface is an articulatingsurface. In some embodiments, the second bearing surface is anarticulating surface. In some embodiments, the first bearing surface andsecond bearing surface geometries are the same. In some embodiments, thefirst bearing surface and second bearing surface comprise differentgeometries, with such differences as illustrated between FIGS. 34 and 36or the superior surface of FIG. 42 and the inferior surfaces of FIGS.44-48.

In some embodiments, the first bearing surface and second bearingsurface geometry are generally convex. In some embodiments, the geometryof the first bearing surface and/or second bearing surface is generallyspherical. In some embodiments the first bearing surface geometry isgenerally flat to spherical.

In still other embodiments, only the second bearing surface geometry isgenerally flat to spherical. Alternately the second bearing surfacegeometry may be generally flat with radiused edges. Still further thesecond bearing surface geometry may be generally flat and transitioningto a proportionately large spherical radius to replicate a worn orsurgically prepared endplate surface. Such variations in the secondbearing surface, (typically the inferior surface), would be advantageouswhen addressing the surgical desire to match or closely replicate asurface that is either severely abraded due to (compressive) arthriticwear, or a surface that is surgically scraped by the surgeon to removeosteophytes, and disrupted or torn cartilage, resulting in a less thannatural radius of curvature on this surface which might otherwiseinterfere with the function of the implant. One skilled in the art willalso recognize that the inferior is often easier for surgeon to accesswith instruments, depending on the surgical approach used.

In even further embodiments, the first bearing surface and secondbearing surface comprise slightly increasing arcuate radii of curvaturefrom the outer radial edge surface to the central axis. In someembodiments, the arcuate radii of curvature of the first and secondbearing surfaces are essentially mirror imaged about a centraltransverse plane.

By way of example, in any one of the embodiments described herein, theradius of curvature R of the endcap is calculated by the formula:R=H/2+W²/8H; wherein H is the height of the arc of the implant; W is thewidth of the implant (in either the sagittal or coronal plane).

In any of the embodiments described herein the width of the implant orchord of the arc, (in either the sagittal or coronal plane) has a rangebetween 17.0 mm and 69.0 mm, whereas the height of the spherical radiusof curvature of the of the bearing surface comprises a range between 0.1mm (generally flat) and 5.0 mm.

In addition, the spherical radius can be variable within the fullspectrum of these ranges, in both planes simultaneously, meaning that agiven bearing surface can have more than one spherical radius at anygiven measurement point. Ideally, for manufacturing purposes, thespherical radii would be nearly constant for the majority of the surfacearea (i.e.: ≥60%) in any one axis, before blending to the radial edges.However, the inventors recognize that the spherical radius may becustomized to better accommodate different spherical radii of theendplate surface near the center of the endplate versus the sphericalradius near the perimeter of the endplate (the epiphyseal rim),accounting for central endplate wear, abrasion or surgical preparation,as may be typically seen on the inferior endplate. Customized, variablespherical radii can now readily be achieved in manufacturing processesthat utilize CNC multi-axis machining centers.

The differences between the spherical curvatures in the sagittal andcoronal planes would be further exaggerate in an ideally ellipticalshaped or irregular Reuleaux polygon shaped implant, wherein theanterior-to-posterior width of the device would be narrower than themedial-to-lateral width, potentially requiring a larger coronalspherical radius and narrower sagittal spherical radius.

To further illustrate the variability of the geometry in someembodiments, the second outer surface geometry is generally flat withradiused edges. In others, the second outer surface geometry isgenerally flat to convex. Still further, in some embodiments, the secondouter surface geometry is generally flat and transitioning to aproportionately large spherical radius, as described above, to replicatea worn or surgically prepared endplate surface, typically representingthe inferior endplate in a spinal joint.

As used herein, the anatomic body planes are the imaginary flat surfacesthat are used to define a particular area of anatomy. The most commonones being: The Frontal or Coronal Plane which vertically divides thefront and back halves of the entire body; The Median, Midsagittal orSagittal Plane—which vertically divides the left and right sides of theentire body; and The Transverse or Horizontal Plane—which divides thebody (horizontal to the ground) at the waist (top and bottom halves ofthe body). In this specification, the terms are applied universally toany bone in the spine.

In some embodiments, the first bearing surface and second bearingsurface are centered about a central axis, wherein the implant surfacesare essentially symmetric about both the coronal and sagittal planes.Further still, the at least one conic protrusion is centered about thecentral axis. In other embodiments, the at least one conic protrusion islocated off-center from the central axis. An example of this can be seenin FIGS. 28-30.

Still further, in some embodiments, the implant comprises ananterior-posterior (front to back) dimension that is greater than theoverall arcuate height of the implant. This dimensional configurationcan be provided in a range and may be represented by a ratio wherein theanterior-posterior dimension to the overall arcuate height is at least1.01:1; is at least 1.1:1; or is at least 1.2:1, etc., for non-limitingexample, as illustrated in FIGS. 4 and 5, 6 and 7, or 8 and 9.

Further still, in some embodiments, the implant comprises amedial-lateral dimension that is greater than the overall arcuate heightof the implant. This dimensional configuration can also be provided in arange and may be represented by a ratio wherein the medial-lateraldimension to the overall arcuate height is at least 1.01:1; is at least1.1:1; is at least 1.2:1, etc., for non-limiting example.

In some embodiments, the implant comprises at least two protrusions. Inother embodiments, the implant comprises exactly two protrusions. Instill other embodiments, the implant comprises at least one protrusionon at least one bearing surface, wherein the at least one protrusion isconic.

Still further, in some embodiments, the at least one conic protrusion isa truncated cone 61, 62, 71 comprising a base diameter 64, 65 with awider girth at the base than the top 66, 67 and may further comprise aninner void 63, 72 as illustrated in any of the non-limiting examples ofFIGS. 16-27. In those embodiments where the conic protrusion includes aninner void, the void may be a blind hole 73, 74, or it may be a voidthat extends through the entire implant 63. In preferred embodiments theconic protrusions, and holes or voids would be concentric about acentral axis. In other embodiments neither the conic protrusions norvoids would be concentric, or centered about a central axis.

Referring now to FIGS. 16-18, an embodiment 60, comprises truncatedconic protrusions 61 and 62 respectively located at the center or theapproximate center of superior and inferior surfaces 68, 69respectively, similar to protrusions 13 and 14 (FIG. 1) except that theyhave a larger base perimeter (64, 65) and truncated top (66, 67) toaccommodate a thru-hole 63 sized to allow for bone or tissues ingrowth,or graft material that is intended to provide additional capture,further minimizing the potential for expulsion. The perimeter or crosssection geometry of the thru-hole can either be a circle, preferred formanufacturing reasons, or any other geometry. The size of the thru-hole63 is a size that accommodates and promotes bone or tissue ingrowth.This size, generally, will typically have a sectional area rangeequivalent to diameters ranging from 2.0 mm to 10.0 mm, but may belarger or smaller. The surface finish of the thru-hole 63 may betextured to provide better adhesion properties for ingrowth of tissue. Asurgeon may decide to fill this through hole with harvested bone chipsor synthetic bone (or other graft material) with or without bone growthstimulators.

Another embodiment 70, represented by FIGS. 19-21, comprises aprotrusion 71 with a blind hole 72 on just one surface 75 that can beeither the superior or inferior surface of the implant. The geometry ofthe protrusion is similar to 61 and 62 previously mentioned (FIG. 17)and the average sectional width 73 of blind hole 72 is similar topreviously mentioned thru-hole 63. The depth 74 of the blind hole may ata minimum be about 0.5 mm, and at a maximum depth being approximately1.0 mm from the point of breaking through the opposite surface 76. Thesurface finish of the blind hole 72 may be textured to provide betteradhesion properties for ingrowth of tissue. Additionally, the hole maybe inversely tapered to promote a better anchoring reservoir that wouldresist pullout of the anchoring materials under natural loadingconditions. This embodiment can be incorporated with any of thepreviously mentioned perimeter geometries (22, 31 and 41) with superiorand inferior surfaces positioned either approximately parallel to eachother when viewed perpendicular to the coronal plane, or at a lordoticangle 47. A surgeon may decide to fill this blind hole with harvestedbone chips or synthetic bone (graft material) with or without bonegrowth stimulators.

Referring now to FIGS. 22-24, embodiment of the invention 80,illustrates one example of the previous illustration wherein a surgeoncan utilize a biocompatible tether or wicking tether 81. Likewise,implant 90, shown in FIGS. 25-27 illustrates another example where theblind hole 72 contains a biocompatible tether or wicking tether 91. Thebiocompatible “wick” or “tethering” devices 81 and 91 function in afashion similar to an artificial ligament, by promoting growth of newtissue between the disc implant and the adjacent vertebral body(s)creating an additional stabilizing structure for the spinal jointsegment. The surface finish of the blind hole may be textured to providebetter adhesion properties for ingrowth of tissue. Additionally, thehole may be inversely tapered to promote a better anchoring reservoirthat would resist pullout of the anchoring materials under naturalloading conditions. Alternatively, the tether could be cross-pinned (notshown) through the side wall of the implant to fix it within theimplant. The tethers 81 and 91 could be fabricated from any number ofmaterials, including autologous tissues, allograft tissues, xenograftstissues, or a variety of artificial, man-made synthetic graft materials.These materials could also be impregnated or treated with stem cells,chondrocytes, proteins or other growth promoting factors to further thelikelihood of a successful graft.

Referring now to FIGS. 28-30, another embodiment 100 of the invention issimilar to discs 10, 30, and 40 except there are two or more protrusions101 on one bearing surface 102, that can either be the inferior surfaceor the superior surface, as well as one protrusion 103 on the othersurface 104. This embodiment is designed to allow articulation on onlyone side of a vertebral joint; against the surface 104, having only oneprotrusion 103. The multiple protrusions 101, each of which shaped asprevious defined protrusions 13 and 14, can be located anywhere on thesurface 102 and are intended to prevent this surface 102 from movingrelative to the adjacent vertebral endplate (as depicted in FIG. 3-20 or21). One of the protrusions 101 can be located at the center of surface102 with one or more protrusions located off center. Or all of theprotrusions can be located in areas other than the center of surface102.

Alternatively, referring now to FIGS. 31-35, embodiment 110 is similarto that depicted by 100 except that there are no protrusions on surface113. The surface 113 is similar to previously defined articulatingsurface 52. Still further, another embodiment 120 (FIG. 36), comprises aroughened, coated or porous surface 122. Surface roughness, (such asgrit blasted, textured, porous, laser sintered, roughened porous spraytitanium or as coated pyrolytic carbon); coatings (such asHydroxyapatite); porous coating (such as porous titanium, tantalum orsilicon nitride); or porous formation (such as chemical etching of thesurface); on the bearing surface(s) are meant to promote fibrous or bonyon-growth and/or ingrowth as a means of further anchoring the device.These surface treatments are those commonly known to the industry andone skilled in the art.

In any one of the embodiments described herein, at least one protrusionis configured to puncture the adjacent endplate when the implant ispositioned between vertebrae. In some embodiments, the heights of thevarious protrusions may not all be the same. For example, as shown inFIGS. 37 & 39, the truncated cone 131 may be set at one height, whereasthe other smaller diameter conic protrusions 133 may have a differentheight. As just noted, embodiment 130 features a combination of anenlarged central protrusion 131 with a blind hole 132 in addition to oneor more protrusions 133 on the surface 135, comprising combined featuresof previous embodiments. All versions of this embodiment can beincorporated with any previously mentioned perimeter geometries (22, 31and 41) with superior and inferior surfaces positioned eitherapproximately parallel to each other when viewed perpendicular to thecoronal plane or at a lordotic angle 47, (FIGS. 11& 12). Additionally,each variation of this embodiment can be incorporated with a roughened,coated or porous surface 122 (FIG. 36), as previously described.

Alternate configurations of this implant include embodiments comprisingirregular polygon shapes, or irregular Reuleaux polygons. One suchembodiment 140 is now illustrated in (FIGS. 40-43) comprises a fin orkeel shaped abutment 142 on the surface 141 that could be either theinferior surface or the superior surface. This abutment is intended toprevent articulation of surface 141 against the adjacent vertebral bodyendplate (either 20 or 21 in FIG. 3) while allowing the opposite surface143 to freely articulate against its adjacent vertebral body endplate.As with previously mentioned protrusions, the height 144 of the finabutment 142 will be sufficient to penetrate the cartilage endplate(either 20 or 21) and into the vertebral body (either 18 or 19respectively), while not being tall enough to create difficulty duringimplantation. This height can range between 0.3-2.5 mm, and ideallyranges between 0.6-1.5 mm. The length 145 of the abutment 142 can rangeanywhere between 20%-80% of the implant anterior to posterior (A/P)dimension 146. The fin sectional geometry 147 is generally rectangularwith beveled surfaces 151 at the apex 148 or any geometry where the base149 is larger than the apex 148. The non-articulating surface 141 caneither be relatively smooth, or comprise a textured, roughened, porouscoated, or a sintered porous surface 152 (FIG. 44) to further ensurethat the surface does not articulate relative to the adjacent vertebralendplate when implanted.

In some embodiments, at least one of the first bearing surface and thesecond bearing surface comprises at least one fenestration. As usedherein, a fenestration is any hole, window or opening, of any size orshape, in the surface of the implant. The at least one fenestration maybe circular or non-circular in profile, and/or a blind void or hole 162,181. The fenestration may also be a ridge and groove combination 171-174in a surface. Or more than one fenestration may be present, with eachhaving a different configuration 181, 182, 184. Examples of variousnon-limiting configurations of fenestrations are illustrated in FIGS.45-47.

Embodiment 160 (FIG. 45) employs two or more cavities 162, in additionto a keel, on surface 161 in order to promote bony ingrowth, furtherimmobilizing the implant relative to the adjacent vertebral bodyendplate when implanted. The section or perimeter of each cavity caneither be circular, as preferred for manufacturing reasons, or be anypolygon or closed curve geometry The diameter or equivalent diameter canrange from 0.5 mm to 3.0 mm. The depth of the cavity can range between0.5 mm to a depth that is within 1.0 mm of breaking through the oppositesurface.

Yet another embodiment 170 (FIG. 46) features one or more ridges 171protruding from surface 174 that further immobilize surface 174 fromarticulating against the adjacent vertebral endplate when implanted. Thetrajectory 173 of the ridge sectional geometry 172 can be a line or anycurve whose path is not parallel to the length 145 of the fin abutment142. A first preferred orientation is perpendicular to the fin. A secondpreferred orientation is between 15°-45° offset from perpendicular,pointing toward the anterior of the device. In this orientation,insertion into the joint space is enhanced, while removal orunintentional anterior movement is hindered. The section 172 of theridge(s) can be triangular or any geometry where the base of the sectionmerging with surface 174 is greater than the apex or tip of the ridge.The height of the ridge section projected from the surface 174 can rangefrom 0.3 mm to 0.8 mm. The width of the base of the ridge(s) can rangebetween 0.5 mm to 1.5 mm. Yet another version of this embodiment 180(FIG. 47) combines the cavities 181 and ridges 182. Versions 160, 170and 180 of this embodiment can either have relatively smooth surfaces ortextured surfaces as defined by 152. All versions of fins, fenestrationsand ridges illustrated in these embodiments can be incorporated with anyof the previously mentioned perimeter geometries (22, 31 and 41) withsuperior and inferior surfaces positioned either approximately parallelto each other when viewed perpendicular to the coronal plane or at alordotic angle 47, (FIG. 12).

In any one of the embodiments herein, at least one of the first bearingsurface and the second bearing surface is polished, wherein the at leastone polished bearing surface has a surface finish ≤4 RMS. In a preferredembodiment, the at least one of the first bearing surface and the secondbearing surface is an articulating surface.

In some embodiments, exactly one of the surfaces is an articulatingsurface and at least a portion of the other of the surfaces is atextured surface. In some embodiments, at least a portion of at leastone of the first surface and the second surface is textured.

Still further, in other embodiments, at least a portion of both of thefirst surface and the second surface is textured, as illustrated innon-limiting FIGS. 36, 44, 60, 61, and surfaces 122, 152. In somepreferred embodiments, such as FIGS. 60, 61 both of the first surfaceand the second surface is a non-articulating surface, wherein at least aportion of both of the first surface and the second surface is a fusionsurface. In such a preferred embodiment, at least a portion of the firstsurface or the second surface comprises a surface finish ≥125 RMS.Typically, these surfaces are textured and/or porous to some degree.

In any one of the embodiments described herein, one or more of thebearing surfaces comprise a textured surface, wherein the texturedsurface is a roughened surface configured to receive a fixationcompound. Such surfaces may be machined textured, laser finishedtextured surfaces, chemically treated (i.e.: acid etched), or comprise ametallurgically applied coating. In some embodiments of the implants,one or more bearing surfaces may comprise a textured surface, whereinthe textured surface is a porous coating. In some embodiments, theporous coating is intended to replicate the pore structure of cancellousbone. Typical materials for textured and porous coated surfaces include:CPTi, CoCr beads, tantalum, porous PEEK, etc. In general, a coating canbe configured from any chemically compatible material that will securelybond to the base material of the implant. Alternatively, anon-articulating surface may comprise one or more fenestrations, whereina fenestrated surface is a surface configured to receive a fixationcompound.

As defined herein, a fixation compound may comprise a biologic orpolymerizing cements. Biologic examples include morselized bone graph orpaste, or any comparable bone-graft-substitute material, cells,proteins, biologic glue, tissue sealants and fibrin sealants. Examplesof polymerizing cement include polymethyl methacrylate (PMMA orPlexiglas), glue, cement, epoxy, bonding agent, fixative, paste,adhesive, adherent, binding agent, sealant, mortar, grout or anycompatible synthetic, self-curing organic or inorganic material used tofill up a cavity or to create a mechanical fixation. Alternatively, thefixation compound may comprise a combination of any one of theaforementioned biologic and polymerizing cements. Fixation compounds maybe used to permanently fix an implant to a surface; or alternately maybe used to permanently bond assembled (implant) components together.

Provided herein is a disk-like implant adapted for placement betweenadjacent vertebral endplates comprising: a first endcap having a firstouter surface and first inner surface and a first outer radial edge; asecond endcap having second outer surface and second inner surface and asecond outer radial edge, an intermediate core having an upper surfaceand lower surface configured to mate between the first inner surface andthe second inner surface; at least one protrusion on at least one endcapsurface, wherein the at least one protrusion is configured to contact aportion of at least one adjacent vertebral endplate.

Referring now to non-limiting examples illustrated in FIGS. 48-59, arenumerous examples of disk-like (or alternatively, “disc-like”) implantscomprising a first and second endcap and an intermediate core.

In any one of the following embodiments, the first endcap surface andsecond endcap surface are each configured to have an external bearinggeometry configured to conform to the geometry of adjacent endplatesurfaces.

In any one of the embodiments, the first inner surface and second innersurface is configured to mate with the intermediate core,

In some embodiments, the first outer surface is an articulating surface.In some embodiments, the second outer surface is an articulatingsurface.

In some embodiments, the first outer surface and second outer surfacegeometries are the same and comprise constant arcuate radii ofcurvature. In other embodiments, the first outer surface and secondouter surface comprise different geometries. In still other embodiments,the first outer surface and second outer surface geometry are generallyspherical.

In some embodiments, only the first outer bearing surface geometry isgenerally spherical. In others, only the first outer bearing surfacegeometry is generally spherical to flat. In some embodiments, the secondouter bearing surface geometry is generally spherical. In still others,the second outer bearing surface geometry generally spherical to flat.In still others, the second outer bearing surface geometry is generallyflat with spherical radiused edges blending to the sides. In any one ofthe embodiments described herein, the spherical geometry may vary fromone anatomic plane to another plane.

Referring now to FIGS. 48-51, the articulating implant 190 comprises ashock-absorbing core 191 sandwiched between the first and second endcaps194. This core 191 imparts a cushioning effect in place of the naturaldisc nucleus. The durometer of the shock-absorbing core/ring would beselected to provide anatomically appropriate stiffness to replace thenatural disc stiffness, yet be selected from polymers having highcompressive wear and fatigue resistance. This core 191 would bepermanently bonded to the internal end cap surfaces 195 of the two endcaps 194 of implant 190 eliminating the potential for any relativemovement at the interface 197 between the core 191 and the end caps 194.The height or thickness 192 of the intermediate core 191 comprises arange between 1.0 mm and 15.0 mm. The height 193 of the individualendcaps 194 will comprise a range between 1.0 mm 6.0 mm. Together, theheight of the insert 191 plus two end caps 194 will comprise the overallarcuate height 199 of the implant. Preferred embodiments would comprisecervical implants with an overall arcuate height 199 similar to 23defined in FIG. 5, ranging between 4.0-12.0 mm. Similarly, preferredembodiments of lumbar implants would have an overall height rangingbetween 8.0-24.0 mm. Ideally, the superior and inferior bearing surfaces196 would be highly polished, as well as one protrusion 198 centered onboth surfaces 196, as previously described.

In another version of a non-limiting articulating embodiment 200 (FIGS.52-55), the endplates incorporate a pocket 201 in the interior surfaceof the end caps 202 and corresponding protrusions 204 on both surfacesof the shock-absorbing core 203. The intent of the core protrusions 204and end cap pockets 201 is to further prevent the possibility ofmovement of the core 203 relative to the end caps 202 in addition topermanent bonding of the interfaces between these components. The height205 of both end cap pockets 201 will range from 0.5 mm to 1.5 mm. Thediametral size and height of the core protrusions 204 can range from aloose slip fit to a line-to-line interference fit (as is commonly knownin the industry) with the end cap pockets 201. As previously noted, thecore would be permanently bonded to the mating endcaps. Ideally, thesuperior and inferior bearing surfaces 206 would be highly polished, aswell as one protrusion 207 centered on both surfaces 206, as previouslydescribed.

In still another non-limiting embodiment, not displayed, the previousembodiment (200) would comprise and inverse configuration, wherein therewould are pockets in the core and corresponding protrusions in the endcaps, in addition to permanent bonding of the interfaces.

In yet another non-limiting embodiment, illustrated by implant 210(FIGS. 56-58) the endcaps comprise a sliding fit mechanism comprising ofa protrusion 211 that engages a corresponding hole 212 in hub 218, witha sliding fit. The purpose of this sliding fit mechanism is to minimizeshear stress on the polymer or hydrogel core 213 and improve fatiguelife of this core component. The shock-absorbing core 213 has acorresponding thru-hole 214 that will provide clearance with the hub 218sliding fit mechanism. This core 214 would be permanently bonded to theend caps 215 at the interfaces 220 created by the interior surfaces ofthe endcaps 219 and the superior and inferior surfaces 217 of theshock-absorbing core 213. All versions of this embodiment can beincorporated with any of the previously mentioned perimeter geometries(22, 31 and 41) with superior and inferior surfaces positioned eitherapproximately parallel to each other (as illustrated in FIG. 11) whenviewed perpendicular to the coronal plane, or at a lordotic angle 47,(as illustrated in FIG. 12). Ideally, the superior and inferior bearingsurfaces 216 would be highly polished, as well as one protrusion 221centered on both surfaces 216, as previously described.

In some variations of embodiment 210 (FIGS. 56-58), the first protrudingattachment means is a protruding cylinder with a hole, centered aboutthe central axis. In some embodiments, the first protruding attachmentmeans is a protruding polygon having three or more sides with a hole,centered about the central axis. In some embodiments, the hole is apolygon having three or sides. Still further, in some embodiments, thehole may be a blind hole or a tapered hole. In some embodiments, thetapered hole comprises a Morse taper.

In corresponding variations of embodiment 210, the second protrudingattachment means is a protruding cylinder with a hole, centered aboutthe central axis. In some embodiments, the second protruding attachmentmeans is a protruding polygon with a hole, centered about the centralaxis. In some embodiments, the hole is polygonal. Still further, in someembodiments, the hole may be a blind hole or a tapered hole. In someembodiments, the tapered hole comprises a Morse taper.

It is further understood that although the non-limiting examples of theimplants illustrated herein for these configurations (FIGS. 48-59) arecircular in plan-view, an equally preferred or ideal planar geometry ofthese implants is elliptical or an irregular Reuleaux polygon, such asillustrated in FIG. 63.

In any of the aforementioned embodiments, the first inner surface andthe second inner surface are textured surfaces, wherein the texturedsurface is surface configured to receive a fixation compound intended tobond an intermediate core to the implant.

In any one of the embodiments, the intermediate core is configured to beshock-absorbing and biocompatible. In some embodiments, the intermediatecore is a hydrogel. In some embodiments, the intermediate core is apolymer.

In any one of the embodiments, the intermediate core upper surface isbonded to the first inner surface and the intermediate core lowersurface is bonded the second inner surface, and the bond is permanent.

In any one of the embodiments, the first inner surface and the secondinner surface are essentially parallel to each other about a centraltransverse plane.

In some embodiments, the first inner surface and the second innersurface are not parallel, and are inclined toward each other about acentral transverse plane, (not shown). More specifically, implants 190,200 (FIGS. 48-55), may be configured to have an intermediate core, withinclined superior and inferior surfaces intended to replicate specificlordotic or kyphotic spinal angles.

Ideally, any of the circular embodiments described throughout thisspecification comprise diametral dimensions in the range of 17.0 mm-45.0mm, (corresponding to the anticipated A/P dimension [sagittal planedepth] of the vertebral endplate), whereas the height of the sphericalradius of curvature for the endcap bearing surface comprises a rangebetween 0.1 mm (generally flat) and 5.0 mm.

Alternatively, in other preferred embodiments described throughout thisspecification comprising elliptical or irregular Reuleaux polygonconfigurations, the implants comprise corresponding M/L dimensions(coronal plane, width) in the range of 24.0 mm-69.0 mm, in addition tothe A/P (sagittal plane, depth) and height of the spherical radius ofcurvature dimensions described previously.

Additionally, in some embodiments the first outer surface and secondouter surface are inclined to each other about a central transverseplane. The angle of inclination, as measured in the sagittal plane, isrepresentative of the desired degree of lordosis (or kyphosis) to beincorporated into the implant. Ideally, any of the circular, ellipticalor irregular Reuleaux polygon-shaped implants described throughout thisspecification comprise a lordosis included angle between the ranges of0°-20°.

In some embodiments, the inclined angle, or lordosis (or kyphosis) angleis incorporated into the intermediate core, i.e.: FIGS. 48-55. In otherembodiments, the inclined angle, or lordosis (or kyphosis) angle isincorporated into the endcaps, i.e.: FIGS. 56-59.

In still other embodiments, the arcuate radii of curvature of the firstand second outer surfaces are essentially mirror imaged about a centraltransverse plane.

In some embodiments, the implant comprises an anterior-posteriordimension that is greater than the overall arcuate height of theimplant. In some embodiments, the ratio of the anterior-posteriordimension to the overall arcuate height is at least 1.01:1. In someembodiments, the ratio of the anterior-posterior dimension to theoverall arcuate height is at least 1.1:1. In still other embodiments,the ratio of the anterior-posterior dimension to the overall arcuateheight is at least 1.2:1. In still other embodiments, the ratio of theanterior-posterior dimension to the overall arcuate height is at least1.5:1, or at least 2.0:1.

In some embodiments, the implant comprises a medial-lateral dimensionthat is greater than the overall arcuate height of the implant. In someembodiments, the ratio of the medial-lateral dimension to the overallarcuate height is at least 1.01:1. In other embodiments, the ratio ofthe medial-lateral dimension to the overall arcuate height is at least1.1:1. In still other embodiments, the ratio of the medial-lateraldimension to the overall arcuate height is at least 1.2:1. In stillother embodiments, the ratio of the medial-lateral dimension to theoverall arcuate height is at least 1.5:1; at least 2.0:1, at least3.0:1, or at least 4.0:1.

In some embodiments, at least one of the first outer surface and thesecond outer surface is a bearing surface. Still further, in someembodiments, at least one of the first outer surface and the secondouter surface is a polished bearing surface, wherein the at least onepolished bearing surface has a surface finish ≤4 RMS. Further still, atleast one of the first outer surface and the second outer surface is anarticulating surface.

In some embodiments, exactly one of the bearing surfaces is anarticulating surface and at least a portion of the other of the surfacesis a textured surface. In some embodiments, at least a portion of atleast one of the first outer surface and the second outer surface istextured. In still other embodiments, at least a portion of both of thefirst outer surface and the second outer surface is textured. Stillfurther, in some embodiments, both the first outer surface and thesecond outer surface is a non-articulating surface. In some of thepreceding embodiments, the textured surface comprises more than oneprotrusion configured to contact a portion of at least one adjacentvertebral endplate.

In other embodiments, at least a portion of both of the first outersurface and the second outer surface is a fusion surface. In someembodiments, the fusion surface comprises more than one protrusionconfigured to penetrate a portion the adjacent vertebral endplate.

In some of the preceding embodiments, at least a portion of the firstouter surface or the second outer surface comprises a surface finish≥125 RMS. In some embodiments, a surface comprising a surface finish≥125 RMS is a textured or porous coated surface or a surface intended tomimic a cancellous bone structure. In some embodiments, a textured orporous coated surface is a surface configured to receive a fixationcompound.

Referring now to two non-limiting examples shown in FIGS. 60-62, 64, 65,are fusion or salvage implant embodiments. Salvage implants refer tothose instances where a former implant (of any type) has failed orrequires replacement. Fusion or salvage implants may incorporate variousforms of traditional fusion augmentation hardware such as screws andplates and may also include other supplemental augmentation such asstabilizing structures attached to the adjacent vertebrae to furthercapture the implant within the vertebral joint. These supplementalaugmentation stabilizing structures may include allograft, autograft,synthetic graft materials, or combinations thereof. Additionally thesesupplemental augmentation stabilizing structures may further beaugmented with growth promoting materials such as collagen, fibrin,chondrocytes, stem cells, peptides or growth hormones or other growthpromoting factors.

In any one of the preceding fusion embodiments, the implant is circularin the transverse (horizontal) plane.

In any one of the preceding embodiments, the implant is elliptical inthe transverse (horizontal) plane, wherein the medial-lateral (M/L)dimension is greater than the anterior-posterior (A/P) dimension.

In any one of the preceding embodiments, the implant is an irregularReuleaux polygon in the transverse (horizontal) plane, wherein the majormedial-lateral (M/L) dimension is greater than the majoranterior-posterior (A/P) dimension.

In any one of the preceding fusion embodiments, the implant is alsoconfigured with an intermediate core (not shown), configured to be ashock absorber that would mimic the natural disc, while also replacinglost disc height.

In any one of the preceding embodiments, the implant is configured foruse in the spine of a human, wherein the implant is a spinal discimplant.

In any one of the preceding embodiments, the implant is configured foruse in the spine of a human, wherein the implant is a spinal fusionimplant.

In any one of the preceding embodiments, the implant is configured foruse in the spine of a human, wherein the implant comprises anarticulating surface on one side and a fusion surface on the oppositeside.

In any one of the preceding embodiments, the implant is a unitary discimplant comprising no independent moving components.

In some of the preceding embodiments, the implant is a unitary discimplant comprising no independent moving components, as assembled.

In some embodiments, the implant is a joint implant, having applicationsin artificial limbs, robotics, or other joints and mechanisms. In someembodiments, the implant is a medical implant having applications forveterinary applications. In still other preferred embodiments, theimplant of the subject specification is a human medical implant intendedfor the spine.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

What is claimed is:
 1. A spinal disc implant comprising: a firstinflexible endcap comprising a first generally spherical articular outerbearing surface comprising wear resistant material, centered about alongitudinal axis in a sagittal plane and a first inner non-articularsurface; a second inflexible endcap centered about the longitudinal axiscomprising a second non-articular, textured outer bearing surface and asecond inner non-articular surface; an intermediate core comprising abiocompatible hydrogel or a biocompatible polymer, having an uppernon-articular surface and a lower non-articular surface bonded betweenthe first inner non-articular surface and the second inner non-articularinner surface; and a first rotational, penetrating protrusion centeredabout the longitudinal axis extending from the first outer bearingsurface.
 2. The spinal disc implant of claim 1, wherein the first outerbearing surface and the second outer bearing surface each generallyconform to a natural endplate geometry of a first adjacent vertebraljoint surface and a second adjacent vertebral joint surfacerespectively.
 3. The spinal disc implant of claim 1, further comprising:at least a second penetrating protrusion centered about the central axisextending from the second outer bearing surface; and the secondnon-articular, textured outer bearing surface comprises a fusionsurface.
 4. The implant of claim 3, wherein the second non-articular,textured outer bearing surface comprises at least one of: a porousstructure; a porous coating; a grit blasted texture; a laser sinteredtexture; an etched surface; a roughened porous spray titanium; ahydroxyapatite coating; one or more ridges; one or more cavities; one ormore fenestrations; a surface finish ≥125 RMS and a combination thereof.5. The implant of claim 4, further comprising: a generally flat secondouter bearing surface geometry, transitioning to a spherical radiussurface geometry near the radial edge.
 6. The spinal disc implant ofclaim 5, wherein the first endcap outer bearing surface and secondendcap outer bearing surface are inclined to each other about a centraltransverse plane.
 7. The implant of claim 3, wherein the first articularbearing surface and penetrating protrusion are polished bearing surfacescomprising a surface finish ≤4 RMS, and the second non-articular,textured outer bearing surface and the at least second penetratingprotrusion comprise a surface finish ≥125 RMS.
 8. The implant of claim1, wherein the first endcap outer bearing surface and second endcapouter bearing surface geometries are the same.
 9. The implant of claim1, wherein the first endcap outer bearing surface and second endcapouter bearing surface comprise different geometries.
 10. The implant ofclaim 9, wherein the first endcap outer bearing surface and secondendcap outer bearing surface geometries are selected from a groupconsisting of: constant arcuate radii of curvature; increasing arcuateradii of curvature from the outer radial edge to the central axis;decreasing arcuate radii of curvature; different arcuate radii ofcurvature; and mirror imaged arcuate radii of curvature.
 11. The spinaldisc implant of claim 10, wherein the arcuate radii of curvature of thefirst endcap outer bearing surface and second endcap outer bearingsurface are essentially mirror imaged about a central transverse plane.12. The spinal disc implant of claim 9, wherein the first endcap outerbearing surface and second endcap outer bearing surface are inclined toeach other about a central transverse plane.
 13. The spinal disc implantof claim 1, further comprising a generally circular planar shape aboutthe longitudinal axis.
 14. The spinal disc implant of claim 1, furthercomprising a noncircular planar shape about the longitudinal axis. 15.The spinal disc implant of claim 1, further comprising an ellipticalplanar shape about the longitudinal axis.
 16. The spinal disc implant ofclaim 1, further comprising: a Reuleaux polygon planar shape comprisingthree or more odd number of sides; or an irregular Reuleaux planar shapecomprising three or more odd number of sides with one or more sideshaving straight side edges, curved side edges or combinations ofstraight and curved side edges.
 17. The implant of claim 1, wherein thefirst outer bearing surface is selected from a group consisting of:pyrolytic carbon, titanium nitride, tantalum, cobalt, chromium, alumina,zirconia oxide, silicon carbide, silicon nitride, stainless steel, PEEK,Delrin, diamond, and diamond-like material.
 18. The implant of claim 1,wherein the first inner non-articular surface and the second innernon-articular surface are selected from a group consisting of: a concavesurface; a convex surface; a non-flat surfaces; a raised surface; arecessed surface; a stepped surface; and a textured surface.